1. Field of the Invention
The invention relates to a rotary supporting base, more particularly to a rotary supporting base for a display device.
2. Description of the Related Art
Referring to FIGS. 1 and 2, a conventional rotary supporting base 900 for a liquid crystal display 800 is shown to include a stationary lower ring base member 93 and a rotatable upper ring base member 91. The lower ring base member 93 is formed with two arcuate sliding slots 935 in diametrically opposite positions. The upper ring base member 91 is disposed on the lower ring base member 93 and is rotatable relative to the lower ring base member 93 about a rotary axis. The upper ring base member 91 has a bottom surface 910, and inner and outer peripheral walls 911, 913 extending downwardly from the bottom surface 910. The bottom surface 910 is formed with a plurality of positioning plates 915 arranged along the inner and outer peripheral walls 911, 913. The positioning plates 915 arranged along the inner peripheral wall 911 cooperates with the inner peripheral wall 911 so as to confine a plurality of positioning grooves 917 engaging slidingly an inner ring rib 937 formed on a top surface of the lower ring base member 93, while the positioning plates 915 arranged along the outer peripheral wall 913 cooperate with the outer peripheral wall 913 so as to confine a plurality of positioning grooves 917 engaging slidingly an outer ring rib 937 on the top surface of the lower ring base member 93, as shown in FIG. 1. The bottom surface 910 of the upper ring base member 91 is further formed with two screw sockets 918 that correspond to the sliding slots 935 in the lower ring base member 93, respectively. Two screw fasteners 95 extend through the sliding slots 935 in the lower ring base member 93 and engage the screw sockets 918 in the upper base member 30 to fasten the upper ring base member 91 to the lower ring base member 93.
In the aforesaid configuration, the allowable extent of rotation the upper ring base member 91 depends on the lengths of the sliding slots 935 in the lower ring base member 93. As such, the extent of rotation of the upper ring base member 91 is limited when the sliding slots 935 are too short. On the other hand, when the sliding slots 935 are long enough to permit a larger extent of rotation of the upper ring base member 91, the structural strength of the lower ring base member 93 is affected adversely. Furthermore, vibration of the upper ring base member 91 during rotation of the liquid crystal display 800 may result in disengagement between the screw fasteners 95 and the screw sockets 918 and in rapid wearing of the screw fasteners 95.